Scroll apparatus for fluid compression or expansion are typically comprised of two upstanding interfitting involute spirodal wraps which are generated about respective axes. Each respective involute wrap is mounted upon an end plate and has a tip disposed in contact or near-contact with the end plate of the other respective scroll wrap. Each scroll wrap further has flank surfaces which adjoin in moving line contact, or near contact, the flank surfaces of the other respective scroll wrap to form a plurality of moving chambers. Depending upon the relative orbital motion of the scroll wraps, the chambers move from the radially exterior end of the scroll wraps to the radially interior ends of the scroll wraps for fluid compression, or from the radially interior end of the respective scroll wraps for fluid expansion. The scroll wraps, to accomplish the formation of the chambers, are put in relative orbital motion by a drive mechanism which constrains the scrolls to non-rotational relative motion. The general principles of scroll wrap generation and operation are discussed in numerous patents, such as U.S. Pat. No. 801,182.
Numerous attempts have been made to develop co-rotational scroll apparatus. Such apparatus provides for concurrent rotary motion of both scroll wraps on parallel, offset axis to generate the requisite orbital motion between the respective scroll wrap elements. However, most commercially successful scroll apparatus to date have been of the fixed scroll-orbiting scroll type due to various difficulties in achieving success with co-rotating scroll apparatus.
In addition to the energy consumed by the additional bearing surfaces typically found, other energy losses can occur. As the scrolls rotate, fluid around and in the vicinity of the scrolls is "fanned" by the scroll members. After the scrolls have been rotating for a period of time, the fluid adjacent the scrolls develops a swirling or centrifugal flow field around the periphery of the scrolls due to the motion of the scroll members. This presents a substantial difficulty when the scroll members are contained in a shell or enclosure. The flow field thus developed increases the total energy requirement for the scroll apparatus, since both the scrolls and the fluid are rotated, and the overall efficiency of the scroll apparatus is reduced.
It has also been difficult to obtain and control adequate lubricant flow through the scroll wraps of a co-rotational scroll apparatus. In many applications such as refrigeration and air conditioning, the scroll apparatus is employed as a gas compressor in a closed circuit system. Lubrication of the compressor in such systems is typically accomplished by providing a lubricant which is miscible in the gas to be compressed, and circulating all or a portion of this lubricant in the closed system. The effect of the centrifugal flow field is to precipitate this miscible lubricant out of the gas, leaving effectively no lubricant available to flow through the scroll wraps of the scroll apparatus and filling the container in which the scrolls rotate with lubricant. This lubricant accumulating in the container also tends to be swirled by the scrolls, requiring additional energy input to the scrolls.
In certain co-rotational scroll apparatus, lubricant is also provided to the bearings supporting the scroll elements. This lubricant also contributes to the lubricant accumulation in the container as it flows from the bearings after having lubricated them.
Therefore it is an object of the present invention to provide a co-rotational scroll apparatus which is efficient in operation.
It is another object of the present invention to provide such a scroll apparatus as will be suitable for use in closed circuit systems such as refrigeration systems.
It is yet another object of the present invention to provide a co-rotational scroll apparatus as will maintain a controlled, effective and adequate flow of lubricant therethrough.
It is yet another object of the present invention to provide such a scroll apparatus as will be simple and inexpensive and suitable for mass production.
These and other objects of the present invention will be apparent from the attached drawings and the description of the preferred embodiment that follows hereinbelow.